1. Field of the Invention
The present invention relates to a disc cartridge in which a disc-like recording medium such as an optical disc, a photomagnetic disc and a magnetic disc is accommodated rotatably in a disc-accommodating chamber of a cartridge case. More specifically, the present invention relates to a disc cartridge in which by rotating an intermediate shell for forming a disc accommodating chamber with an upper shell or a lower shell, a pair of shutter members are opened/closed so as to open/close an opening portion and when it is opened, part of the disc-like recording medium is exposed through the opening portion.
2. Description of the Related Art
Conventionally, as a disc cartridge in which a disc-like recording medium allowing recording/reproduction of information such as audio, video and computer data is accommodated rotatably in a cartridge case thereof, a disc cartridge having a structure shown in FIG. 42 has been well known. This disc cartridge 1 contains an additionally writable photomagnetic disc 4 allowing information such as computer data to be additionally written therein and has an external shape shown in FIG. 42.
This disc cartridge 1 comprises a cartridge case 2 composed of a pair of an upper shell 2a and a lower shell 2b, a photomagnetic disc 4 accommodated rotatably in the disc accommodating chamber 3 of the cartridge case 2 and the like. A top face and a bottom face of the cartridge case 2 have upper and lower opening portions 5 extending from the center portion to a side thereof. The opening portions 5 can be opened/closed by a shutter member 6 capable of sliding along a side. This shutter member 6 is always urged in a direction of closing the opening portion 5 by a spring (not shown). Reference numeral 6a denotes a pressing member for preventing a front end of the shutter member 6 from slipping out.
A center hub 7 formed of metal in a circular shape is provided in the center of the photomagnetic disc 4. This center hub 7 is disposed at a position corresponding to an inside end of the opening portion 5, that is, substantially in the center of the cartridge case 2. A turntable provided on the main body of an information recording/reproducing apparatus is loaded on this center hub 7. Then, the center hub 7 is chucked by the turntable, so that the photomagnetic disc 4 is driven at a predetermined speed (for example, constant linear speed). By means of a photomagnetic pickup unit whose head portion is inserted into the opening portion 5, recording and reproduction of information signal from/into the photomagnetic disc 4 are carried out.
In the conventional disc cartridge having such a structure, the shutter member 6 for opening/closing the opening portion 5 is formed to have a U-shaped section and this shutter member 6 is fit to a side of the cartridge case 2 such that the shutter member 6 is slidable along that side to open/close the opening portion 5. Thus, because a large gap is generated between the cartridge case 2 and the shutter member 6, it is difficult to block invasion of minute dirt, dust and the like.
In the recent trend of increased capacity of the optical disc and intensified recording density, narrowed pitches in recording patterns and an increase in line density have been accelerated. If dust or dirt invades onto a recording face of the optical disc or photomagnetic disc, reading or writing beam may be intercepted or normal reading/writing of information may be disabled by damage on the information recording face. Thus, in the conventional disc cartridge, as shown in FIG. 42, the shutter member 6 formed to have the substantially U-shaped section is mounted slidably on a side of the cartridge case 2 and by moving the shutter member 6 along the side, the opening portion is opened/closed so as to protect information recording face of the optical disc or the like.
Because of the trend of further increased capacity and intensified recording density, minute dust and dirt, which hardly affect conventionally, influence reading and writing of data more seriously. However, the shutter member formed to have the above-described substantially U-shaped section is incapable of blocking the infiltration of such minute dust and dirt. If the minute dust or dirt infiltrating into the cartridge case 2 is attached to the information recording face of the photomagnetic disc 4, the information recording face is damaged by this dirt or dust, so that proper reading and writing of information are disabled.
Further, because in the conventional disc cartridge 1, the shutter member 6 is located at a position where a user is likely to touch, he may slide the shutter member 6 by mistake to open the opening portion 5. Further, because the shutter member 6 is always urged in the direction of closing the opening portion 5 by a spring (not shown), not only the spring is needed as a component, but also it takes much labor and time to assemble the spring, thereby leading to poor assembly efficiency and productivity of such a disc cartridge.
The present invention has been achieved to solve the above-described problem and therefore, an object of the invention is to provide a disc cartridge in which an intermediate shell is held rotatably by an upper shell and a lower shell without using a spring while a pair of the shutter members are opened/closed by rotation of the intermediate shell, the disc cartridge being capable of being mounted on a recording/reproducing apparatus not only when the pair of the shutter members are completely closed, but also incompletely closed or completely opened, the opening portion being opened securely upon loading of the disc cartridge and the pair of the shutter members being closed securely when discharged from the recording/reproducing apparatus, thereby securing high dust resistance and airtightness.
To achieve the above object, according to a first aspect of the present invention, there is provided a disc cartridge comprising: cartridge case in which a disc accommodating chamber is formed between an upper shell and an intermediate shell or between the intermediate shell and a lower shell by overlaying the upper shell, the intermediate shell and the lower shell, while the intermediate shell is supported rotatably by the upper shell and the lower shell; disc-like recording medium which is accommodated rotatably in the disc accommodating chamber while part of the disc-like recording medium is exposed through an opening portion provided in the intermediate shell, the lower shell or the upper shell; and a pair of shutter members mounted on the intermediate shell, capable of opening/closing the opening portion, wherein at least one of the upper shell and the lower shell is provided with an operating window for rotating the intermediate shell and a driven portion, which is engaged with a shutter opening/closing means passing outside the operating window for rotating the intermediate shell up to a predetermined position, is provided on an external peripheral face of the intermediate shell.
According to a second aspect of the present invention, there is provided a disc cartridge according to the first aspect wherein the pair of the shutter members is comprised of a combination of two plates of the same shape while the pair of the shutter members are disposed symmetrically on a side face of the intermediate shell so as to close the opening portion, and a side portion of each of the shutter members is supported rotatably by the intermediate shell while the other side portion thereof is engaged slidably with the lower shell or the upper shell, so that the pair of the shutter members opens/closes the opening portion by relative rotations of the intermediate shell, the lower shell and the upper shell.
According to a third aspect of the present invention, there is provided a disc cartridge according to the first aspect wherein the shutter opening/closing means comprises a rack portion reciprocating outside the operating window, an initial action convex portion disposed before and after the rack portion and a stopper convex portion, and the driven portion comprises a gear portion which meshes detachably with the rack portion, a rack portion which is an initial shutter opening/closing means disposed on both sides in the circumferential direction of the gear portion and an empty shift portion which releases engagement with the gear portion provided between the initial action convex portion and the stopper convex portion, the driven portion being provided with a sliding portion for generating a relative sliding corresponding to the empty shift portion.
According to a fourth aspect of the present invention, a rotation joint portion is comprised of a shaft portion provided on any one of the shutter members acting in pair and the intermediate shell and a fitting hole provided in the other component. A shift joint portion is comprised of a guide groove provided in the shutter members and the lower shell or the upper shell and an operating convex portion provided in the other component. By moving the operating convex portion along the guide groove based on rotation of the intermediate shell, a pair of the shutter members are opened/closed.
According to a fifth aspect of the present invention, there is provided a disc cartridge according to the fourth aspect wherein the stopper convex portion is formed higher than the rack portion while a set position concave portion is provided in a tooth root circle of the gear portion.
In the disc cartridge of the first aspect, comprising the cartridge case containing the disc accommodating chamber, the disc-like recording medium and a pair of the shutter members, the driven portion provided on the external peripheral face of the intermediate shell faces the operating window provided on at least one of the upper shell and the lower shell. If the shutter opening/closing means passes outside this operating window, the driven portion engages with this shutter opening/closing means so as to rotate the intermediate shell up to a predetermined position. Thus, a gap between the pair of the shutter members and the cartridge case is reduced so that minute dust and dirt become difficult to enter into the disc-accommodating chamber. Consequently, dust resistance of the cartridge case is intensified and irrespective of whether the pair of the shutter members are opened or closed, the opening portion is opened surely when the disc cartridge is loaded on the recording/reproducing apparatus. When the disc cartridge is discharged from the recording/reproducing apparatus, the opening portion is kept closed surely.
In the disc cartridge of the second aspect of the present invention, two sheets of the same shape are disposed so as to close the opening portion while one side portion of each is supported rotatably on the intermediate shell and the other side portion is engaged with the lower shell or the upper shell slidably. A pair of the shutter members is opened/closed by a relative rotation of the intermediate shell and the lower shell or the upper shell. Consequently, while the area of each shutter member is reduced, it is possible to open/close a wider-area opening portion thereby leading to increase of opening/closing efficiency of the opening portion. At the same time, reduction of the size and thickness of the disc cartridge can be achieved and a pair of the shutter members can be opened/closed smoothly and surely.
In the disc cartridge of the third aspect of the present invention, the shutter opening/closing means comprises the rack portion, the initial action convex portion and the stopper convex portion. The driven portion of the intermediate shell comprises the gear portion, the initial action concave portion and the set position concave portion. Consequently, if the shutter opening/closing means is passed outside the operating window, the initial action convex portion or the rack portion engages with the initial action concave portion or the gear portion, so that the intermediate shell is rotated up to a predetermined position. As a result, the intermediate shell can be rotated surely up to the predetermined position and a pair of the shutter members is opened/closed smoothly by the rotation of the intermediate shell, thereby achieving the opening/closing of the opening portion.
In the disc cartridge of the fourth aspect of the present invention, the empty shift portion is provided between the rack portion, the initial action convex portion and the stopper concave portion and correspondingly, the driven portion is provided with the sliding portion. Consequently, the rack portion and the gear portion can be synchronized with each other so as to rotate the intermediate shell securely to a predetermined position. As a result, a pair of the shutter members can be opened/closed securely so as to achieve the opening/closing of the opening portion.
In the disc cartridge of the fifth aspect of the present invention, because the stopper convex portion is higher than the rack portion, when the stopper convex portion engages with the set position concave portion, the intermediate shell can be fixed at a predetermined position as if it is locked, so that the intermediate shell is protected from being rotated by vibration or the like.